Carriage drive for high speed printer

ABSTRACT

A carriage drive for a high speed dot matrix printer, including a reversible stepping motor connected through a clutch to a rotary driven member that is in turn connected by a belt to the printer carriage. The clutch remains engaged as long as the motor operates in a character-spacing direction, but reversal of the motor disengages the clutch and permits a torsion spring to drive the carriage back to a line start position. Near the end of the return movement, a flywheel decelerator absorbs the kinetic energy of the carriage and then utilizes that kinetic energy to prevent bouncing of the carriage.

[ 1 June20,1972

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Primary Examiner-Robert E. Pulfrey Assistant Examiner-Eugene H. EickholtAttorney-Kinzer, Dom and Zickert [57] ABSTRACT A carriage drive for ahigh speed dot matrix printer, including a reversible stepping motorconnected through a clutch to a 405 rotary driven member that is in turnconnected by a belt to the printer carriage. The clutch remains engagedas long as the motor operates in a character-spacing direction, butreversal of the motor disengages the clutch and permits a torsion springto drive the carriage back to a line start position. Near the end of thereturn movement, a flywheel decelerator absorbs the kinetic energy ofthe carriage and then utilizes that kinetic energy to prevent bouncingof the carriage.

197/64 14 Chins, 14 Drawing Figures [51] Int. Cl.19/02 197/60, 62, 64,65, 66, 68,

[22] Filed: Sept. 10, 1970 [21] AppLNo: 71,051

[52] [58] FieldofSearch......................

[56] References Cited UNITED STATES PATENTS 3,532,20510/1970 3,586,1476/1971 Hoffman..... 3,444,976 5/1969 Anderson 2,129,650 9/1938PATENTEUJUR 20 m2 SHEET 10F 9 Inventor-s We Hter J Zerzner Ragmond E.Kran 5 Q51 and fi-Hornei gs PATENTEDJUH20 m2 qllllllllllllllIllIIIIIlllllllll l nnuolun nunnu 'HHHIHHIHIII IIIIIHHIIIHIIInventors wa l'l'er J. Zennex' Rm mond E.Kran

B3, Kin u, Dow M zidwvb fl'ltorn e%6 PATENTEnJuuzo m2 SHEET 3 BF 9 III mmm

SHEET U 8F 9 Inventors Walter J. Zenner' Raq mond E.Kr m' DM and'fl-H-ornew H PATENTEDJun 20 m2 PATENTEUJum 1972 3, 670,861 saw 5 OF 9Fig.7

Inventors walt'et J. Zennel" Reign-10nd E.Kran

B ,Dam and zit/k 2 a zq-Hrorn e 35 ran PATENTEUJux 20 I972 SHEET 6 BF 9PATENTEDJUNZO m2 3, 670, 861

SHEET 8 OF 9 133 21 Invent-o rs v Walter J. Zenner Ragxnond E.Krcu15orrzegs CARRIAGE DRIVE FOR HIGH SPEED PRINTER BACKGROUND OF THEINVENTION In a wide variety of different kinds of high speed printers, acarriage is moved in incremental steps along a given path in the courseof the printing operation. In some typewriters, in conventionaltelegraphic printers, and in many other printing machines the incrementsof advance are usually equal to one character width. In other machines,and particularly in some forms of dot matrix printers, the incrementalcarriage movements are much smaller. For example, in a dot matrixprinter the carriage may advance eight distinct steps in the formationof each character, five steps for the formation of five individualcolumns of dots that form a character and three additional steps toafford a blank space between that character and the next character inthe line.

In any of these printing machines, the overall speed and efi'rciency ofthe printer is dependent to a considerable extent on a rapid return ofthe carriage from the end of one line to the starting point forbeginning the next line. During the carriage return operation, it isusually necessary to advance a sheet of paper or a paper web by one linespace in the printing machine. Except for the time required for a linespace operation, however, the entire carriage return interval iscompletely wasted.

In some high speed printers, spring return mechanisms have been used toreturn the carriage rapidly from the end of one line to the beginning ofthe next line. These spring devices can be constructed to afford a highspeed carriage return movement, materially reducing the wasted time. Buta spring return for the carriage frequently creates other problems. Inparticular, when the carriage reaches the end of its return movement,travelling at a high speed, it tends to bounce; if bouncing occurs, itis necessary to wait an additional period of time until it is suppressedor to accept printing irregularities at the beginning of each line.Another difficulty results from the need to release the carriage fromits normal driving connection to the motor or other drive apparatus thatadvances the carriage incrementally from the beginning of the line, inorder to allow operation of the return spring. In general, it is ratherdifficult to adapt conventional clutches or like mechanisms to affordadequately rapid release of the carriage while retaining the capabilityof restoring thenormal incremental drive connection to the carriage assoon as it reaches the beginning line position.

SUMMARY OF THE INVENTION It is a principal object of the presentinvention, therefore, to provide a new and improved carriage drive for ahigh speed printer, and particularly a carriage drive of the kind thatutilizes a spring mechanism to achieve rapid return movement of theprinter carriage from any intermediate position on a line back to aninitial position to start a new line.

. A particular object of the invention is to provide a new and improvedcarriage drive for a high speed printer, especially adapted for use in adot matrix printer, that affords accurate, consistent, and rapidmovement of the carriage in extremely short increments, with severalincrements to each character width. r

Another specific object of-the invention is to provide a new andimproved decelerator for the carriage of a high speed printer thateffectively minimizes any bounce of the carriage as the carriage reachesits initial position, upon return from an advanced position.

Accordingly, the invention is directed to a carriage drive for a highspeed printer of the kind comprising a carriage movable in predeterminedincremental steps along a given path in a character-spacing directionfrom an initial position toward a limit position and movable back alongthat path to its initial position from any position on the path. Thecarriage drive comprises a rotatable drive member and reversible drivemeans, preferably a reversible electrical stepping motor, for rotatingthe drive member in incremental steps in either a normal direction or areverse direction. A rotatable driven member is operatively connected tothe carriage of the printer and is employed to drive the carriage in itscharacter-spacing direction when the driven member is rotated in a firstdirection. The carriage drive includes clutch means for coupling thedrive member to the driven member to rotate the driven member in theaforementioned first direction in response to rotation of the drivemember in its normal direction; the clutch means, however, is actuatableto a disengaged position whenever the drive member is rotated in itsreverse direction. Spring return means are provided for moving thecarriage in its return direction, independently of the drive means,whenever the clutch is disengaged. A carriage decelerator is providedfor engaging and braking the carriage,

as the carriage approaches its initial position. The decelerator alsouses the kinetic energy of the returning carriage to hold the carriagein its initial position, without bouncing, once that position isreached.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a highspeed printer in which the carriage drive of the invention may beemployed;

FIG. 2 is a front perspective view of a high speed printer incorporatingthe carriage drive of the present invention, with the cover and someother parts of the printer stripped away;

FIG. 3 is a rear perspective view of the printer of FIG. 2;

FIG. 4 is a cut away plan view of the printer, with most of the platenand carriage omitted;

FIG. 5 is a sectional side elevation view taken approximately asindicated by line 5-5 in FIG. 2;

FIG. 6 is a detail sectional view of a declerator incorporated in thecarriage drive;

FIG. 7 is a detail sectional view of a clutch and certain sensingswitches included in the carriage drive;

FIG. 8 is a sectional side elevation, partially cut away, takenapproximately along line 8-8 in FIG. 3;

FIG. 9 is a detail, from FIG. 8, showing an alternate operatingcondition;

FIG. 10 is a detail plan view, partly in cross section;

FIG. 1 1 is a detail sectional view taken approximately along line 11-11in FIG.'10;

FIG. 12 is a detail view of a part of the apparatus that has been cutaway in FIG. 8;

FIG. 13 is a front perspective view of a high speed printerincorporating another embodiment of the carriage drive of the presentinvention; and

' FIG. 14 is a side elevation view of the printer of FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 through 12 illustrate ahigh speed printer 20, comprising a dot matrix printer, thatincorporates a carriage drive constructed in accordance with a preferredembodiment of the present invention. Printer 20 comprises a base 21; twovertical side plates 23 and 24 are mounted upon base 21 at the leftandright-hand sides, respectively, of the printer. The spacing between theupper parts of side plates 23 and 24 is effectively maintained by aseries of tie rods that span the distance between the side plates. Theseinclude a rear tie rod 25, an upper tie rod 26, and a lower tie rod 27,joining plates 23and24and base 21 inarigid frame.

may be a part of a continuous web drawn from a roll 33, ex-

tends into the housing 31, around the platen 29, and back out as shownin FIGS. 1 and 5. A separate sheet of paper can be used if desired.

Since printer 20 is a dot matrix printer, it is essential that the paper32 be held tightly against platen 29 at the point of printing impactwithin the machine, in order to avoid perforation of the paper. This isaccomplished in part by a wire bail 34 that extends across the entirewidth of platen 29. The opposite ends of bail 34 are pivotally mountedto the frame of the printer. The right hand end of bail 34, as seen inFIGS. 2 and 10, is pivotally mounted in side plate 24, whereas theopposite end of the bail is pivotally mounted in a bracket 35 that isaffixed to side plate 23. At the end of the bail adjacent plate 24, alug 36 is mounted on the bail; lug 36 is connected to a spring 37, theother end of the spring being connected to a post 38 mounted upon sideplate 24. At the other end of bail 34,-a lug 39 is mounted on the bailand is connected to a spring 41 having its opposite end connected to aprojecting post 42 on bracket 35. Springs 37 and 41 normally maintainbail 34 in firm contact with platen 29, as shown particularly in FIGS.2, and 12. However, the bail can be pivoted away from the platen to asecond stable position, shown by dash outline 34A in FIGS. 5 and 12, tofacilitate renewal of the paper supply for the printer.

Printer 20 also includes a pressure roll assembly 44 that is bestillustrated in FIGS. 4 and 5. The pressure roll assembly comprises apressure rollsupport lever 45 that is pivotally mounted at a centralpoint upon the rear tie rod 25. One end of lever 45 projects downbeneath platen 29. It terminates in a U-shaped bracket 46 in which apressure roll 47 is mounted. At the opposite end of lever 45, a spring48 is connected to the lever, the other end of spring 48 being connectedto base 21. It is thus seen that spring 48 continuously maintains roller47 in firm contact with paper 32, pressing the paper against platen 29(FIG. 5).

A paper guide 51 is also mounted upon tie rod 25 (FIGS. 4 and 5). Guide51 affords a sloped guide surface 52 that guides the .paper web 32 intocontact with platen 29 (FIG. 5). The paper guide 51 terminates at a lip53 (FIGS. 4 and 5) that extends across the entire width of the platen. Aspring 54 connects guide 51 to the pressure roll support lever 45 sothat both members can be displaced from platen 29 simultaneously if thisis necessary or desirable to facilitate clearance of paper jam or formaintenance activities.

At the front of the high speed printer 20, as shown in FIGS. 2, 4 and 5,two carriage guide rails 56 and 57 extend across the printer from sideplate 23 to side plate 24; the two guide rails are located on oppositesides of the lower tie rod 27. A print carriage 60 is mounted upon guiderails 56 and 57 and moves longitudinally of the guide rails, from leftto right as seen in FIG. 2, in printing each line.

As shown in FIG. 5, carriage 60 includes a vertically extending printmagnet support member 61 from which two cantilever upper carriagesupport rollers 62 project. Each of the carriage support rollers 62includes a pair of spaced flanges 63 that engage the upper surface ofcarriage guide rail 56 to maintain carriage 60 in accurate alignment onthe guide rails, preventing shifting of the carriage in a directionalong the axes of carriage support rollers 62. The free end of each ofthe support rollers 62 is of circular cross sectional configuration andmerely rests upon the other carriage guide rail 57. Each of the twoupper support rollers 62 is preferably formed of molded plastic and isrotatably supported upon a metal cantilever shaft 64 that is mountedupon support member 61.

At the lower end of support member 61, two shafts 65 are mounted uponthe carriage, projecting from support member 61 beneath guide rail 56.On each of the shafts 65 there is a roller 66 that engages 'the lowersurface of guide rail 56 (FIG. 5). In addition, each shaft 65 isprovided with an extension 67 that carries a second roller 68 whichengages the bottom surface of guide rail 57. The rollers 66 and 68 areeach vertically aligned with one of the upper support rollers 62,maintaining carriage 60 in fixed accurate alignment with respect to theguide rails 56 and 57 throughout the movement of the carriage along thepath defined by the guide rails.

The particular dot matrix utilizes in printer 20, in the reproduction ofalphabetic and numeric characters, is a 5 X 7 matrix, seven dots highand five dots wide. A full column of seven dots is reproduced in oneoperation, requiring seven in- -dividual dot printing devices invertical alignment. Two of these dot printing devices are illustrated inFIG. 5. The upper dot printing device shown therein comprises a printmagnet 71 mounted upon the curved outer surface 72 of support member 61;magnet 71 projects through an opening 70 in support member 61, theopening 72 being shown in FIG. 2. An elongated, stiff needlelike printwire 73 projects from print magnet 72 through a print wire guide 74,terminating at a point immediately adjacent the surface of platen 29.Guide 74 is mounted upon a bracket 75 that is supported upon a pair ofcantilever print guides 76 mounted upon carriage support member 61. Thelower-most printing device, also illustrated in FIG. 5, comprises asimilar print magnet 77 mounted upon the arcuate outer surface 72 ofsupport member 61. Print magnet 77 actuates an elongated needle-likeprint wire 78 which, like needle 73, projects from the print magnetthrough the needle guide 74 and terminates at a point immediatelyadjacent the surface of platen 29. The remaining five printing deviceshave been omitted from the drawing; the apertures for mounting theremaining printing devices on support member 61 are shown in FIG. 2.

There is a projection 81 extending inwardly from the lower end ofsupport member 61 (FIG. 5). An actuator member 82 is mounted uponprojection 81 and extends downwardly from carriage 60. Actuator 82 isutilized to actuate a series of control switches, as describedhereinafter, and is also employed as a connecting member in the carriagedecelerator that is a part of the present invention, as describedhereinafter.

At the left-hand side of printer 20, as seen in FIGS. 2 and 4, anadjustable stop 83 is mounted upon side plate 23. Stop 83 is acantilever device that projects from side member 23 toward the carriage,terminating in a replaceable cushion member 84 formed of rubber or otherlike resilient material.

, The carriage drive of the present invention, in printing machine 20,comprises a reversible electric stepping motor 86 mounted upon a pair ofvertical posts 87 as shown particularly in FIGS. 3, 4 and 5. The shaft88 of motor 86 extends in a vertical direction, and the lower end of theshaft is journalled in a bearing 89 mounted upon base 21 (FIG. 5). Thelower end of shaft 88 carries a pulley 91 that engages a toothed drivebelt 92 of the kind'commonly referred to as a timing belt. Belt 92,

at its other end, engages a rotatable drive pulley 93 that is.

mounted upon a short vertical shaft 94 as shown in FIGS. 4, 5 and 7. Anidler support lever 95 is also pivotally mounted upon shaft 94. Lever 95and pulley 93 are formed with complementary spaced parallel walls and ahelical spring 96 is mounted in'the space between members 93 and 95, asbest shown in the sectional views of FIGS. 5 and 7. One arm 98 of theidler support lever includes a downwardly extending shaft portion 99upon which an idler gear 101 is mounted by means of a retainer 102 (FIG.7). 'The idler support lever 95 is also connected to a spring 104 thatis anchored to side plate 24. A detent spring 103, mounted on base 21,projects into alignment with idler gear 101, but does not normallyengage the idler.

Spring 104 normally biases the idler support member 95 in a clockwisedirection, maintaining idler 101 in meshing engagement with a drivengear 105 mounted upon a vertically extending shaft 106. Idler 101 isalways in mesh with a pinion gear 107 that is formed as an integral partof the rotatable drive pulley 93. Thus, idler 101 normally affords apositive driving connection between the rotatable drive member 93 andthe rotatable driven member 105; however, this drive connection can beinterrupted quite easily and quickly by rotation of the idler supportlever 95 as described more fully hereinafter.

The driven gear 105 is affixed to an elongated sleeve 108 that ismounted upon shaft 106 by appropriate bearings, preferably ball bearingsas illustrated in FIG. 5. The upper end of sleeve 108 includes a pulleysection 109 that engages a carriage driven belt 110. The carriage drivebelt 110 is preferably a toothed flexible drive belt of the kindgenerally referred to as a timing belt One end of the carriage drivebelt 110 is fastened to the right-hand side of the print carriage 60.The other end of the carriage drive belt extends around a pulley 111 andis secured to the left-hand side of carriage 60, as shown particularlyin FIGS. 2 and 4.

Pulley 111 is mounted upon a vertical shaft 112 and is part of anelongated sleeve 113 substantially similar in construction to the sleeve108. A torsion spring 114 is affixed to one end of sleeve 113, and theother end of torsion spring 114 is secured to base 21. The orientationof torsion spring 114 is such that, as carriage 60 moves from left toright in the printing of a line, the torsion spring is wound tighter andtighter. Torsion spring 114 comprises a spring return means for movingcarriage 60 back to its initial position, in engagement with stop 83, tobegin each new line of printing.

As carriage 60 moves from left to right across printer 20, along thepath defined by guide rails 56 and 57, actuator'82 serves to indicatearrival of the carriage at certain critical positions. At the right-handend of printer 20, a sensing switch element 116 projects upwardlythrough base 21 in position to engage actuator 82 (see FIGS. 4 and 7).Sensing switch element 116 defines the right-hand limit of travel forcarriage 60. To the left of sensing switch element 1 16, there isanother sensing switch element 117 that also projects upwardly throughbase 21 in position to engage actuator 82 on carriage 60. Sensing switchelement 1 17 is located at an arbitrarily defined position from whichthe carriage should be returned to the initial position at stop 83 oncethe printing of a word is completed. In one form of printer 20, using a48 character line, sensing switch element 117 has been located toidentify the completion of the printing of a total of 40 characters.Another sensing switch element 118 projects upwardly through base 21 atthe lefthand end of the path of movement of carriage 60. Sensing switchelement 118, shown in FIGS. 4 and 6, is engaged by actuator 82 to signalthe completion of a carriage return movement, being engaged by actuator82 when the carriage has been returned to its initial position inengagement with stop 83.

The line space mechanism for printer 20 is best illustrated in FIGS.8-11, although parts of this mechanism also appear in other views. Theline space mechanism comprises a solenoid 121 having an armature 122upon which a U-shaped plunger 123 is mounted. A shaft 124 extends beyondplunger 123 and is engaged in a guide 125 in a fixed guide bracket 126.The U- shaped bracket 123 engages the lower end 128 of an operatinglever 129 that is pivotally mounted on a short shaft 131 supported uponside plate 23. The lower end 1280f operating lever 129 carries a pin 132to which a spring 133 is connected; the other end of spring 133 isconnected to a post 134 mounted upon side plate 23 (FIGS. 8 and 9).

The upper end of operating lever 129 is bifurcated and engages a pin 135on a rocker arm 136. Rocker arm 136 includes an extension 137 thatcarries a pin 138. A pawl 139 is pivotally mounted upon pin 138. Ahelical biasing spring 141 is mounted upon an extension of pin 138; oneend of the spring is affixed to the pin and the other end is engaged inan extension 142 of pawl 139. A fixed upper stop 152 and a fixed lowerstop 153 are mounted on side plate 23, extending outwardly from the sideplate above and below the pawl.

Rocker arm 136 is rotatably mounted upon the end of platen shaft 28adjacent side plate 23. It is positioned immediately adjacent a detentwheel 143 that is affixed to the platen shaft 28. A press fit,supplemented with adhesive, may be employed. The detent wheel 143 isprovided with a series of teeth 144 positioned in alignment with andengaged by pawl 139. The teeth 144 on detent wheel 143 are also engagedby a detent roller 146 mounted upon a lever 147 that is pivotallymounted upon a shaft 148 affixed to side plate 23.'Detent roller 146 ismaintained in engagement with detent wheel 143 by a spring 149 havingone end connected to the bottom of lever 147 and the opposite endconnected to a post 151 mounted upon side plate 24 (FIGS. 3 and 8).

The carriage drive of the present invention includes a deceleratorsystem '160, best illustrated in FIGS. 3-6.

Decelerator 160 comprises a low-inertia carriage-engaging meansincluding an operating lever 161 that is pivotally mounted on a post 162affixed to base 21. The end of lever 161 that projects toward the frontof the printing machine 20 is bifurcated to afford a sensing element162A and a restraining element 163; the sensing element 162A is normallydisposed in the path of the actuator 82 of the printing machine carriageas shown in FIG. 4. Operating lever 161 is normally maintained in theposition illustrated in FIG. 4 by a biasing spring 164.

The operating lever 161 of decelerator 160 includes an arm 165 thatterminates in a gear segment 166. Gear segment 166 is disposed inmeshing engagement with a driven gear 167, FIG. 4, that is a part of ahigh-inertia acceleration-resisting means for controlling carriagedeceleration. As shown in FIG. 6, gear 167 is mounted upon a post 169that is affixed to and projects vertically upwardly from base 21. Arelatively large and heavy flywheel 171 is rotatably mounted upon thecentral portion of gear 167. A pair of felt washers 172 and 173 aredisposed upon the top and bottom surfaces, respectively, of flywheel 171and are keyed to gear 167. The felt washers 172 and 173 are engaged bytwo mounting washers 174 and 175, respectively. The entire assembly ismaintained in good frictional contact by a spring washer 176, interposedbetween washer 174 and an additional washer 177; a pair of retainerrings 178 complete the high-inertia acceleration-resisting assembly.

In considering the operation of printing machine 20, and particularlythe carriage drive of the printing machine which constitutes the subjectmatter of the present invention, the best starting point is at thebeginning of a line, with the carriage 60 displaced to the extremeleft-hand end of its path in contact with the rubber bumper 84 on theadjustable stop 83 (FIG. 4). With the carriage in this position,actuator 82 is in engagement with the left-hand limit switch 118. Thisis the initial position for the imprinting of each line of characters bythe printer.

To start printing, motor 86 is energized to rotate shaft 88 in aclockwise direction, as viewed in FIG. 4, driving belt 92 in thedirection indicated by the arrows. This is the normal direction ofrotation for motor 86 and the nonnal direction of movement for belt 92for printing operations. Motor 86 is a stepper motor and moves inpredetermined incremental steps, so that the movement of its shaft 88,belt 92, and the remainder of the carriage drive always occurs inclosely controlled incremental steps as the carriage performs itscharacter spacing movements along guides 56 and 57 The normal movementof belt 92, as indicated by the arrows, causes the rotatable drivemember comprising pulley 93 and gear 107 to rotate in a clockwisedirection. Accordingly, idler 101 is driven in a counterclockwisedirection, and the idler drives gear in a clockwise direction. Thus,belt is driven in a character spacing direction, as indicated by thearrows in FIGS. 2 and 4, in response to the clockwise rotation of thedriven member 105 in the drive system that connects motor 86 to carriagedrive belt 110.

As long as appropriate energizing signals are received by motor 86, anduntil it is necessary to return the carriage to its initial position tobegin a new line, the drive system steps carriage 60 along platen 29,from left to right, as described above. In a typical 5 X 7 dot matrixprinter, five character-space steps are used for the actual imprintingof each alphabetic, numeric, or other character. Usually, energizingsignals are supplied to motor 86 in groups of eight, with the additionalthree increments being utilized for spacing between adjacent characters.When a space between words is required, motor 86 is stepped for the samenumber of increments, or any desired number of signals. This mode ofoperation is facilitated by the provision of sensing switch 117, whichis located a selected number of character spaces from the absolute endof line sensing switch 116 (FIG. 4). When switch 117 is contacted by theactuator 82 on carriage 60, the sensing switch operates a controlcircuit (not shown) for printer 20 that initiates a carriage returnoperation upon the next occurrence of a space signal in thetelegraphicsignal input to the printer. As noted above, switch 117 may be locatedabout eight characters to the left of the sensing switch 116. Switch116, on the other hand, is utilized to initiate a carriage returnoperation instantly upon contact by actuator 82 to prevent loss of copythat could result if carriage 60 were retained at the far right.

In the formation of each character, the individual print wires (e.g.,print wires 73, 78, FIG. print a number of dots upon the paper 32 thatextends around platen 29. The printing operation goes forward at a highrate of speed; in a typical commercial printer, the printing rate isapproximately 600 characters per minute.

When a carriage return is triggered, whether by a received telegraphicsignal or by the operation of either of the switches 1 l6 and 117, thedirection of rotation of motor 86 is reversed. As a consequence, drivebelt 92 is driven in a direction opposite to the arrows (FIG. 4) andpulley 93 starts to rotate in a counterclockwise direction.counterclockwise rotation of pulley 93 causes spring 96 to tighten andgrip the walls of both of the members 93 and 95 (FIGS. 5 and 6). As aconsequence, the idler support lever 95 begins to pivot in acounterclockwise direction to move idler 101 out of engagement with thedriven gear 105 (FIG. 4). In a predetermined number of incremental stepsof motor 86, in its reverse direction, idler 101 is moved to itsalternate position 101A, completely free of gear 105 and in engagementwith detent spring 103. It is thus seen that the idler support member95, idler gear 101, and spring 96 constitute a clutch means that couplesdrive member 107 to driven member 105 to rotate the driven member 105 ina first clockwise direction in response to rotation of the drive member93, 107 in its normal direction; however, this same clutch means isautomatically and promptly actuated to a dis engaged condition inresponse to'reverse rotation of the drive member 107. In one commercialmachine, disengagement of the clutch is effected in four cycles ofoperation of stepper motor 86.

As soon as the clutch mechanism comprising idler 101 is disengaged,carriage 60 is free to move in response to the biasing force supplied bythe torsion'spring 114. Spring 114 has been tightened with eachincrement of movement of carriage 60 during the printing of a line; ifthe carriage has been moved to near the right-hand end of its path, asshown in FIG. 2, torsion spring 114 is tightly wound and exerts aconsiderable force upon belt 110. As a consequence of disengagement ofthe clutch idler gear 101, carriage 60 is rapidly accelerated in areturn direction, back toward its initial position in engagement withstop 83.

As carriage 60 moves in its reverse direction toward stop 83, theactuator 82 on the carriage contacts the sensing extension 162A of theoperating lever 161 for decelerator 160. The continuing movement of thecarriage rotates operating lever 161 in a clockwise direction andimparts a similar rotation to the gear segment 166. This rotates gear167 in a counterclockwise direction, as viewed in FIG. 4.

If the carriage return operation has been initiated with the carriageonly a short distance along the line, as occurs when only a short lineis printed, torsion spring 114 is wound up to only a limited extent andexerts a relatively small force on belt 110. Under these circumstances,carriage 60 moves relatively slowly in the return direction and actuator82 is moving quite slowly when it engages the sensing extension 162A ofoperating lever 161. The slow movement of lever 161 and its gear segment166 results in a relatively slow movement of gear 167. The slow movementof gear 167 offers little resistance to the movement of actuator 82because the acceleration is minimal. Carriage 60 contacts the resilientpad 84 on stop 83 at a slow speed, with little tendency toward bouncing.

On the other hand, when a long line of characters has been imprinted andcarriage 60 starts its return movement from at or near the right-handend of its travel, the torsion spring 114 has been wound much moretightly and applies a much greater force to the carriage. Moreover,under these circumstances there is a greater distance for carriage 60 togain speed. Consequently, actuator 82 strikes sensing extension 162A onoperating lever 161 at a high speed, so that gear 167 is acceleratedrapidly. When this occurs, the force required to impart a correspondingacceleration to flywheel 171 is greater than the frictional couplingbetween gear 167 and flywheel 171. Slipping occurs at the faces of feltwashers 172 and 173; this frictional brake absorbs nearly all of thekinetic energy of the carriage. When the carriage has been slowed downto a speed matching that of the high-inertia flywheel 171, slippingstops and the braking action terminates. Carriage 60 moves freely butslowly back to its initial position.

The continued return movement of carriage 60 brings it into engagementwith the resilient pad 84 on stop member 83. Because the carriage isstill moving at a low speed when it reaches stop 83, the carriage maybounce unless restrained. However, the restraining extension 163 onoperating lever 161 has now been pulled in behind actuator 82, due tothe clockwise movement of lever 161 caused by the return movement of thecarriage (FIG. 4). When carriage 60 starts to bounce, therefore, itimmediately encounters lever extension 163 and starts to pivot lever 161in counterclockwise direction. This bouncing movement is prevented bythe continuing rotational movement of flywheel 171, which continuouslyurges lever 163 toward further clockwise rotation. As a consequence, theremaining kinetic energy of carriage 60 is absorbed as a friction lossat the surfaces bounded by the felt washers 172 and 173 (FIG. 6) and thecarriage is arrested at its initial position without appreciablebouncing.

When the clutch mechanism comprising idler 101 has been disengaged, androtation of the idler has been arrested by detent 103, as describedabove, the clutch remains disengaged until motor 86 is againreversed andresumes rotation in its normal direction. This is accomplished by anelectrical signal initiated when actuator 82 contacts the left-handlimit switch 118, indicating that the carriage has again reaches itsinitial position at the left-hand end of a line. The total minimum timeinterval required for carriage return and re-engagement of the clutchcomprising idler 101 is the time needed for twice the number ofincremental steps utilized for disengaging the clutch. Thus, if theclutch is disengaged in response to four steps of reverse movement ofmotor 86, it is re-engaged by four steps of movement in the normaldirection, restoring the printer to condition for further operation inthe time required for imprinting a single character. The actual elapsedtime may be somewhat longer, depending upon the speed of carriage returnand the time required to complete the second reversal of motor 86.

During the carriage return operation, a line space operation isnecessary to advance a fresh segment of the paper web 32 into positionto receive the next line of printing. In other instances, a separateline space signal may be utilized to initiate a line space operation, aswhen a blank portion of the paper is to be advanced through the printerto begin a new message.

At the start of a line space operation, the line space mechanism is inthe position illustrated in FIG. 8. The line space operation isinitiated by energizing solenoid 121, pulling its armature 122 inwardlyof the solenoid from the position shown in FIG. 8 to that illustrated inFIG. 9. This movement of armature 122 causes the U-shaped portion 123 ofthe solenoid plunger to pull the lower portion 128 and the line spacelever 129 to the left, pivoting lever 129 in a clockwise direction aboutits shaft 131. This drives pin to the right, from the position of FIG. 8to that of FIG. 9 and rotates rocker arm 136 through a limited arc in acounterclockwise direction.

As rocker arm 136 rotates counterclockwise, the engagement of pawl 139with one of the detent teeth 144 drives detent wheel 143counterclockwise. The counterclockwise motion of detent wheel 143 isarrested when pawl 139 engages the upper stop 152. During the rotationof detent wheel 143, the detent roller 146 is driven outwardly againstthe bias of spring 149 and then moves back inwardly into engagement withthe space between the next pair of teeth 144. Thus, the paper advancingmovement is completed, with the mechanism in the position shown in FIG.9.

When the line space operation is complete, solenoid 121 is de-energized.Spring 133 then pulls the lower portion 128 of operating lever 129 backto the right, as seen in FIGS. 8 and 9. This results in acounterclockwise rotation of lever 129 back through a limited are fromthe position shown in FIG. 9 to that illustrated in FIG. 8. The rotationof lever 129 drives pin 135 back to its original position and rotatesrocker arm 136 clockwise from the position of FIG. 9 to that of FIG. 8.In the course of this movement, pawl 139 rides over one of the detentteeth 144 and, as it clears that tooth, the pawl is snapped back intoengagement with the next tooth in response to the bias afforded byspring 141. During this restoration movement, detent roller 146 preventsrotation of detent wheel 143, since the sliding movement of pawl 139 onthe detent wheel does not exert enough force to overcome the biasapplied to roller 146 by spring 149. Accordingly, the detent wheel 143and platen 29 remain in the advanced position with a line space movementcompleted.

The carriage drive incorporated in printer affords a number ofadvantages in operation of the printer. The clutch mechanism comprisingidler gear 101 and its pivotal support 95 disengages rapidly in responseto a reversal of rotation of stepper motor 86, initiating the carriagereturn operation promptly upon the occurrence of conditions requiring acarriage return without requiring a separate motor, solenoid, or otheractuator. Disengagement of the clutch does not result in a loss ofcontrol or timing for the carriage drive, since the clutch is disengagedin a fixed number of steps of motor 86 and re-engagement of the clutchis effected in a corresponding discrete number of motor steps. Thus, thecarriage return operation is completed with the high speed printer fullyconditioned for immediate operation in printing the next character.

Torsion spring 114 affords a rapid carriage return operation with aminimum space requirement for the torsion spring. In cooperation withthe clutch mechanism of idler gear 101, the torsion spring facilitates arapid carriage return operation with minimum loss of time.

Declerator 160 also contributes materially to the advantages of thecarriage drive in high speed printer 20. On a rapid carriage return,originating at the far end of the path of carriage travel, the kineticenergy of the carriage is principally dissipated as frictional heat anda small part is converted into rotational energy of flywheel 171; thatrotational energy is utilized directly to maintain carriage 60 incontact with stop 83 once the carriage reaches the stop. In this manner,the carriage energy is effectively dissipated or usefully employed 'toprevent carriage bounce. The decelerator 160, by minimizing bouncing andvibration, inherently reduces the wear and tear on printer 20 from thecarriage return operation and quickly stabilizes the carriage at itsinitial position at the start of each line, maintaining an evenleft-hand margin in the reproduced copy. Thus, the deceleratorcontributes materially to a rapid, controlled, well-timed turnaround atthe end of the carriage return movement.

Stepper motor 86, as a basic drive element for the carriage drive,contributes to the accurate and consistent advance of carriage 60 alongits operating path. The stepper motor, energized with discrete pulsesthat correspond to the required carriage movements, in combination withtiming belt drives and a gear train, so that there are no friction drivecomponents, makes it possible to maintain complete control over thecarriage movement at all times.

FIGS. 13 and 14 illustrate a high speed printer 220 that is generallysimilar in construction, in many respects, to printer 20, and thatincorporates a carriage drive constructed in accordance with anotherembodiment of the present invention. Printer 220 comprises a base 221,with two vertical side plates 223 and 224 mounted on the base. A platenshaft 228 spans the two side plates and supports a platen 229therebetween. A

bail 234 is normally maintained in engagement with platen 229 and holdsa sheet of paper (not shown) in printing position on the platen. Theprinter may include a paper guide, as described in relation to printer20.

A pair of carriage guide rails 256 and 257 extend across the frame ofprinter 220, between side plates 223 and 224, paral' lel to platen 229.A printing carriage 260 is mounted upon rails 256 and 257. Carriage 260is constructed like carriage of the previous embodiment and is utilizedto support a total of seven dot printing devices, as generally indicatedby the magnetic wire printer devices 271 and 277. In printing a singleline of characters, carriage 260 starts at the left-hand end of guiderails 256 and 257, in contact with a stop member 283, and moves to theright in a series of incremental steps. When a given line is completed,the carriage is returned to its initial position against the stop 283 tobegin the next line.

The carriage drive for high speed printer 220 comprises a motor 286 thatis mounted upon side plate 224. Motor 286 is an electrical steppermotor. The motor is mounted horizontally, with its shaft 288 projectingoutwardly of side plate 224 as shown in FIG. 14.

Motor shaft 288 carries a pinion 291 that is disposed in meshingengagement with a drive gear 292. Drive gear 292 is mounted upon a shaft293 that is in turn mounted to side plate 224. Drive gear 292 is also inmesh with an idler gear 301. Idler gear 301 is rotatably mounted upon ashaft 299 that is mounted upon an idler support member comprising alever 295. The idler support lever 295 is pivotally mounted upon a shaft296 afiixed to side plate 224. A bias spring 304 is connected to theidler support member 295 and biases member 295 toward rotation in aclockwise direction, and toward engagement with an adjustable eccentricstop 298. Idler gear 301 is disposed in meshing engagement with a linefeed gear 331 that is mounted upon the righthand end of platen shaft228. Gear 331 is engaged by a detent spring 303, mounted upon side plate224, that'prevents counterclockwise rotation of gear 331 whilepermitting clockwise rotation.

Idler gear 301 is also disposed in alignment with a driven membercomprising a carriage space gear 305. Gear 305 is mounted upon a shaft332 supported upon side plate 224; a pulley 333 is affixed to gear 305.Pulley 333 is engaged by a drive string 310. From pulley 333, one end ofthe drive string 310 extends around a pulley 334 mounted-on side plate224; from pulley 334, drive string 310 extends to a pulley 311 that ismounted concentrically with and is connected to a torsion spring 314.From pulley 311, drive string 310 is extended to and is connected to theleft-hand side of the printer carriage 2160 (FIG. 13).

As shown in FIG. 14, the other end of drive string 310 extends frompulley 333 around two additional pulleys 335 and 336 that are mountedupon side plate 224. Drive string 310 continues from pulley 336 to theright-hand end of carriage 260 (FIG. 13). 1

At the other end of platen shaft 228 from gear 331, a detent wheel 343is affixed to the shaft (FIG. 13). A detent lever 347 is pivotallymounted upon side plate 223, adjacent detent wheel 343. A detent roller(not shown) is mounted upon lever 347 and is maintained in engagementwith detent wheel 343 by an appropriate spring 349, as in the previousembodiment.

When the high speed printer 220 of FIGS. 13 and 14 is placed inoperation, character space movement of carriage 260, from left to rightalong the path defined by the guide rails 256 and 257, is effected byclockwise rotation of the stepper motor shaft 288. Rotation of shaft 288in a clockwise direction causes pinion 291 to turn drive gear 292 in acounterclockwise direction. The counterclockwise rotation of drive gear292 in turn rotates idler 301 in a clockwise direction.

The idler 301 attempts to turn the line space gear 331 in acounterclockwise direction. However, counterclockwise rotation of gear331 is blocked by the spring detent 303. Consequently, idler gear 301 isdriven, by reaction against gear 331 and against the bias of spring 304,into engagement with the carriage space gear 305. Gear 305 is rotated ina counterclockwise direction and drives the drive string 310 in thedirection indicated by the arrows in both FIGS. 13 and 14. In thismanner, the carriage 260 is stepped rapidly andrepeatedly along theguide rails-256 and 257, printing a line in the manner described abovein connection with printer 20.

As in the previous embodiment, a carriage return operation is initiatedin printer 220 by reversing the direction of rotation of the drivemotor. Thus, to initiate a carriage return, motor 286 is reversed andits shaft 288 is rotated in a counterclockwise direction. This turnsdrive gear 292 clockwise and rotates idler 301 counterclockwise. Linefeed gear 331 can rotate in a clockwise direction and hence is no longerblocked by detent 303. Accordingly, idler 301 is pulled clear ofcarriage space gear 305 by spring 304 and rotates the line feed gear 331in a clockwise direction to afford a line feed operation for the paperin the printing machine.

From the foregoing description, it will be seen that the embodiment ofFIGS. 13 and 14 functions in a manner essentially similar to theembodiment of FIGS. 1-12 except that in the high speed printer 220 ofFIGS. 13 and 14 the line feed operation for the paper, as well as thecarriage return operation, is carried-out directly in response toreverse rotation of the carriage drive motor. Thus, the solenoid 121 isnot necessary in the embodiment of FIGS. 13 and 14.

We claim f 1. In a high speed printer of the kind comprising a carriagemovable in predetermined incremental steps along a given path in acharacter spacing direction from an initial position 7 toward a limitposition and movable along said path in a return direction back to saidinitial position from any position on said path, a carriage drivecomprising:

a rotatable drive member;

reversible stepping drive means for rotating said' drive member, inincremental steps, in a normal direction and in a reverse direction;

a rotatable driven member, operatively connected to said carriage, fordriving said carriage in said character spacing direction in response torotation of said driven member in a first direction; 7 I

clutch means actuatable between an engaged condition and a disengagedcondition, coupling said drive member in operative driving relation tosaid driven member to rotate said driven member in said first directionin response to rotation of said drive member in said normal directionwhen said clutch is engaged, said clutch means being actuatable to itsdisengaged condition in response to reverse rotation of said drivemember;

and spring return means, connected to said carriage, for moving saidcarriage in its return direction independently of said drive means upondisengagement-of said clutch means from said driven member.

2. A carriage drive for a high speed printer, according to claim 1, inwhich said clutch means comprises a rotatable idler member mounted on apivotally movable idler support, said idler support being movable to anengaged position with the idler member coupling the drive member indriving relation to the driven member in response to normal rotation ofthe .drive member, and said idler support being movable to a disengagedposition, in which said idler member is free of at least one of nectedto a pulley engaged by said belt.

. engaging and braking said carriage, as said carriage ap-- proaches itsinitial position, and for using the kinetic energy of nected to saididler support for biasing said idler support toward a position in whichsaid idler gear is in meshing engagement with both said drive gear andsaid driven gear.

5. A carriage drive for a high speed printer, according to claim 3, inwhich said slip coupling comprises a spiral spring interposed betweennested concentric walls of said drive member and said idler supportlever and wound in a direction such that the spring tightens uponreverse rotation of said motor to afford a firm coupling between saidconcentric walls and assure movement of said idler support lever to itsdisengaged position, and further comprising biasing means normallyurging said idler support lever toward its engaged position.

6. A carriage drive for a high speed printer, according to claim 2, andfurther comprising detent means for limiting reverse rotation of saididler member to a given number of incremental steps whenever said drivemeans is driven'in its reverse direction, and in which return of saididler support to its engaged position requires a corresponding number ofincremental steps of rotation of said drive means in its normaldirection.

-'7. A carriage drive for a high speed printer, according to claim 1, inwhich said drive means comprises a subfractional horsepower electricalstepping motor energized by an electrical stepping signal including onecycle for each incremental step of advance required of said carriage.

8. A carriage drivefor a high speed printer, accordingto claim 1, inwhich the operational connection between said driven member and saidcarriage comprises a flexible, beltlike drive connector member, and inwhich said spring return means comprises a torsion spring operativelyconnected to said drive connector member.

9. A carriage drive for a high speed printer, according to claim 8, inwhich said drive connector member is a toothed drive belt and in whichsaid torsion spring has one end con- 10. A carriage drive for a highspeed printer, according to claim 2, and further comprising deceleratormeans, including an operating member projecting into said carriage path,for

the returning carriage to hold said carriage in its initial position,without substantial bouncing, once that position is reached. Y

11. In a high speed printer of the kind comprising a carriage movablealong a given path in a character spacing direction from an initialposition toward a limit position and movable said drive and drivenmembers, in response to reverse rotation of the drive member.

3. A carriage drive for a high speed printer according to claim 2, inwhich the drive member, the idler member, and the driven member are allgears, and in which said idler support comprises a support lever havingone end pivotally mounted in coaxial relation to said drive member andconnected thereto by a slip coupling that tightens only when said drivemember is rotated in its reverse direction, said idler member beingrotatably mounted upon the other end of said support lever.

4. A carriage drive for a high speed printer according to claim 3, andfurther comprising resilient biasing means conalong said path in areturn direction back to said initial position from any position on saidpath, a carriage drive comprising:

precision drive means, coupled to said carriage, for advancing saidcarriage along said path in said character spacing direction; springreturn means, coupled to said carriage, for rapidly moving said carriagein its return direction, independently of said drive means, back to saidinitial position; a fixed stop for said carriage, at said initialposition; and declerator means for engaging and braking said carriage,as said carriage approaches its initial position, and for using thekinetic energy of the returning carriage to hold said carriage in itsinitial position, without substantial bouncing, once that position isreached, said lever and said flywheel, such that during its rapid returnmovement said carriage engages said operating lever at said givenposition and starts rotation of the flywheel to absorb part of thekinetic energy of the carriage, and continuing rotation of the flywheelcauses said lever to press said carriage against said stop.

12. A carriage drive for a high speed printer, according to claim 11 inwhich said coupling between said operating lever and said flywheelincludes a drive gear element mounted on said lever, a driven gearelement mounted coaxially with said flywheel, justaposed engagedfriction members on said flywheel and said driven gear element, andresilient biasing means maintaining said friction members in engagement.

13. In a high speed printer of the kind comprising a carriage movablealong a given path in a character spacing direction from an initialposition toward a limit position and movable along said path in a returndirection back to said initial position from any position on said path,a carriage drive comprismg:

drive means, coupled to said carriage, for advancing said carriage alongsaid path in said character spacing direction;

spring return means, coupled to said carriage, for rapidly moving saidcarriage in its return direction, independently of said drive means,back to said initial position;

a low-inertia carriage-engaging means comprising an operating memberprojecting into position to be engaged by said carriage on its returnmovement;

a high-inertia acceleration-resisting means comprising a flywheel; atwo-way friction coupling between said carriage-engaging means and saidacceleration resisting means; and a fixed stop for interrupting returnmovement of said carriage at said initial position, saidcarriage-engaging means, said acceleration-resisting means and saidfriction coupling conjointly comprising a free-moving high-inertiadecelerator system which intercepts and decelerates said carriage as itapproaches its initial position during return movement, limiting thedecelerating force applied to the carriage to a predetermined maximumand converting a major portion of the kinetic energy of the movingcarriage into heat, said friction coupling maintaining said operatinglever in engagement with said stop, in response to continuing rotationof said flywheel, to prevent bouncing of the carriage. 14. A carriagedrive for a high speed printer, according to claim 13, in which saiddrive means comprises a stepper motor, a drive linkage connecting saidstepper motor to said carriage, and a clutch, interposed in said drivelinkage, for releasing said carriage for return movement in response tosaid spring means.

1. In a high speed printer of the kind comprising a carriage movable in predetermined incremental steps along a given path in a character spacing direction from an initial position toward a limit position and movable along said path in a return direction back to said initial position from any position on said path, a carriage drive comprising: a rotatable drive member; reversible stepping drive means for rotating said drive member, in incremental steps, in a normal direction and in a reverse direction; a rotatable driven member, operatively connected to said carriage, for driving said carriage in said character spacing direction in response to rotation of said driven member in a first direction; clutch means actuatable between an engaged condition and a disengaged condition, coupling said drive member in operative driving relation to said driven member to rotate said driven member in said first direction in response to rotation of said drive member in said normal direction when said clutch is engaged, said clutch means being actuatable to its disengaged condition in response to reverse rotation of said drive member; and spring return means, connected to said carriage, for moving said carriage in its return direction independently of said drive means upon disengagement of said clutch means from said driven member.
 2. A carriage drive for a high speed printer, according to claim 1, in which said clutch means comprises a rotatable idler member mounted on a pivotally movable idler support, said idler support being movable to an engaged position with the idler member coupling the drive member in driving relation to the driven member in response to normal rotation of the drive member, and said idler support being movable to a disengaged position, in which said idler member is free of at least one of said drive and driven members, in response to reverse rotation of the drive member.
 2. A carriage drive for a high speed printer, according to claim 1, in which said clutch means comprises a rotatable idler member mounted on a pivotally movable idler support, said idler support being movable to an engaged position with the idler member coupling the drive member in driving relation to the driven member in response to normal rotation of the drive member, and said idler support being movable to a disengaged position, in which said idler member is free of at least one of said drive and driven members, in response to reverse rotation of the drive member.
 3. A carriage drive for a high speed printer according to claim 2, in which the drive member, the idler member, and the driven member are all gears, and in which said idler support comprises a support lever having one end pivotally mounted in coaxial relation to said drive member and connected thereto by a slip coupling that tightens only when said drive member is rotated in its reverse directioN, said idler member being rotatably mounted upon the other end of said support lever.
 4. A carriage drive for a high speed printer according to claim 3, and further comprising resilient biasing means connected to said idler support for biasing said idler support toward a position in which said idler gear is in meshing engagement with both said drive gear and said driven gear.
 5. A carriage drive for a high speed printer, according to claim 3, in which said slip coupling comprises a spiral spring interposed between nested concentric walls of said drive member and said idler support lever and wound in a direction such that the spring tightens upon reverse rotation of said motor to afford a firm coupling between said concentric walls and assure movement of said idler support lever to its disengaged position, and further comprising biasing means normally urging said idler support lever toward its engaged position.
 6. A carriage drive for a high speed printer, according to claim 2, and further comprising detent means for limiting reverse rotation of said idler member to a given number of incremental steps whenever said drive means is driven in its reverse direction, and in which return of said idler support to its engaged position requires a corresponding number of incremental steps of rotation of said drive means in its normal direction.
 7. A carriage drive for a high speed printer, according to claim 1, in which said drive means comprises a subfractional horsepower electrical stepping motor energized by an electrical stepping signal including one cycle for each incremental step of advance required of said carriage.
 8. A carriage drive for a high speed printer, according to claim 1, in which the operational connection between said driven member and said carriage comprises a flexible, belt-like drive connector member, and in which said spring return means comprises a torsion spring operatively connected to said drive connector member.
 9. A carriage drive for a high speed printer, according to claim 8, in which said drive connector member is a toothed drive belt and in which said torsion spring has one end connected to a pulley engaged by said belt.
 10. A carriage drive for a high speed printer, according to claim 2, and further comprising decelerator means, including an operating member projecting into said carriage path, for engaging and braking said carriage, as said carriage approaches its initial position, and for using the kinetic energy of the returning carriage to hold said carriage in its initial position, without substantial bouncing, once that position is reached.
 11. In a high speed printer of the kind comprising a carriage movable along a given path in a character spacing direction from an initial position toward a limit position and movable along said path in a return direction back to said initial position from any position on said path, a carriage drive comprising: precision drive means, coupled to said carriage, for advancing said carriage along said path in said character spacing direction; spring return means, coupled to said carriage, for rapidly moving said carriage in its return direction, independently of said drive means, back to said initial position; a fixed stop for said carriage, at said initial position; and declerator means for engaging and braking said carriage, as said carriage approaches its initial position, and for using the kinetic energy of the returning carriage to hold said carriage in its initial position, without substantial bouncing, once that position is reached, said decelerator means comprising: an operating lever extending into the path of said carriage at a given position; a flywheel; and a two-way frictional coupling between said operating lever and said flywheel, such that during its rapid return movement said carriage engages said operating lever at said given position and starts rotation of the flywheel to absorb part of the kinetic energy of the carriage, and contInuing rotation of the flywheel causes said lever to press said carriage against said stop.
 12. A carriage drive for a high speed printer, according to claim 11 in which said coupling between said operating lever and said flywheel includes a drive gear element mounted on said lever, a driven gear element mounted coaxially with said flywheel, justaposed engaged friction members on said flywheel and said driven gear element, and resilient biasing means maintaining said friction members in engagement.
 13. In a high speed printer of the kind comprising a carriage movable along a given path in a character spacing direction from an initial position toward a limit position and movable along said path in a return direction back to said initial position from any position on said path, a carriage drive comprising: drive means, coupled to said carriage, for advancing said carriage along said path in said character spacing direction; spring return means, coupled to said carriage, for rapidly moving said carriage in its return direction, independently of said drive means, back to said initial position; a low-inertia carriage-engaging means comprising an operating member projecting into position to be engaged by said carriage on its return movement; a high-inertia acceleration-resisting means comprising a flywheel; a two-way friction coupling between said carriage-engaging means and said acceleration resisting means; and a fixed stop for interrupting return movement of said carriage at said initial position, said carriage-engaging means, said acceleration-resisting means and said friction coupling conjointly comprising a free-moving high-inertia decelerator system which intercepts and decelerates said carriage as it approaches its initial position during return movement, limiting the decelerating force applied to the carriage to a predetermined maximum and converting a major portion of the kinetic energy of the moving carriage into heat, said friction coupling maintaining said operating lever in engagement with said stop, in response to continuing rotation of said flywheel, to prevent bouncing of the carriage.
 14. A carriage drive for a high speed printer, according to claim 13, in which said drive means comprises a stepper motor, a drive linkage connecting said stepper motor to said carriage, and a clutch, interposed in said drive linkage, for releasing said carriage for return movement in response to said spring means. 